Optical mouse

An optical mouse is a computer mouse which uses a light source, typically a light-emitting diode (LED), and a light detector, such as an array of photodiodes, to detect movement relative to a surface. Variations of the optical mouse have largely replaced the older mechanical mouse design, which uses moving parts to sense motion. The earliest optical mice detected movement on pre-printed mousepad surfaces. Modern optical mice work on most opaque diffusely reflective surfaces like paper, but most of them do not work properly on specularly reflective surfaces like polished stone or transparent surfaces like glass. Optical mice that use dark field illumination can function reliably even on such surfaces. Mechanical mouse Though not commonly referred to as optical mice, nearly all mechanical mice tracked movement using LEDs and photodiodes to detect when beams of infrared light did and didn't pass through holes in a pair of incremental rotary encoder wheels (one for left/right, another for forward/back), driven by a rubberized ball. Thus, the primary distinction of “optical mice” is not their use of optics, but their complete lack of moving parts to track mouse movement, instead employing an entirely solid-state system. The first two optical mice, first demonstrated by two independent inventors in December 1980, had different basic designs: One of these, invented by Steve Kirsch of MIT and Mouse Systems Corporation, used an infrared LED and a four-quadrant infrared sensor to detect grid lines printed with infrared absorbing ink on a special metallic surface. Predictive algorithms in the CPU of the mouse calculated the speed and direction over the grid. The other type, invented by Richard F. Lyon of Xerox, used a 16-pixel visible-light with integrated motion detection on the same ntype (5 μm) MOS integrated circuit chip, and tracked the motion of light dots in a dark field of a printed paper or similar mouse pad.